Based on our analysis of Church records, religiously active Mormon males in California and Utah compared with U.S. white males have standardized mortality ratio of 60% for colon cancer, 40% for rectum cancer, and 55% for colorectal cancer. Active Mormons abstain from tobacco, alcohol, and caffeine by Church prescription. However, the specific reasons for their low colorectal cancer rates are unknown. The first objective is to pursue this descriptive mortality data with a prospective epidemiologic study of active California Mormon adults of both sexes. Using a questionnaire survey, demographic, lifestyle, dietary, occupational, and medical history data relevant to colorectal cancer etiology will be obtained on about 20,000 active Mormons, who will subsequently be followed for mortality over a four-year period. Furthermore, Church-based mortality rates covering the years 1960-67 and 1976-79 will be ascertained for all 350,000 California Mormons in order to supplement the existing rates for the years 1968-75. The questionnaire data on dietary and other lifestyle characteristics will be related to the colorectal cancer mortality rates. In addition to intra-Mormon comparisons, active Mormons as a whole will be compared with other California, U.S., and international populations which already have been studied with respect to colorectal cancer. The second objective is to do a correlation analysis of extensive dietary and lifestyle data from the 1971-73 U.S. Health and Nutrition Examination Survey (HANES) with U.S. and California colorectal cancer mortality rates by country of birth and state of residence. Several etiologic variables of interest, including beef, fat, fiber, and beer consumption, will be examined for consistency with international correlations and previous epidemiologic findings. Special emphasis will focus on Spanish Americans born in Mexico, who have colorectal cancer death rates as low as those of active Mormons. The above analyses should yield new understanding of the etiology and prevention of large bowel cancer in the United States.